Re: [PATCH v4 5/6] keys/trusted_keys: establish PKWM as a trusted source

Jarkko Sakkinen
2026-01-19T23:14:47Z

On Thu, Jan 15, 2026 at 03:35:03PM +0530, Srish Srinivasan wrote:
> The wrapping key does not exist by default and is generated by the
> hypervisor as a part of PKWM initialization. This key is then persisted by
> the hypervisor and is used to wrap trusted keys. These are variable length
> symmetric keys, which in the case of PowerVM Key Wrapping Module (PKWM) are
> generated using the kernel RNG. PKWM can be used as a trust source through
> the following example keyctl commands:
>
> keyctl add trusted my_trusted_key "new 32" @u
>
> Use the wrap_flags command option to set the secure boot requirement for
> the wrapping request through the following keyctl commands
>
> case1: no secure boot requirement. (default)
> keyctl usage: keyctl add trusted my_trusted_key "new 32" @u
> OR
> keyctl add trusted my_trusted_key "new 32 wrap_flags=0x00" @u
>
> case2: secure boot required to in either audit or enforce mode. set bit 0
> keyctl usage: keyctl add trusted my_trusted_key "new 32 wrap_flags=0x01" @u
>
> case3: secure boot required to be in enforce mode. set bit 1
> keyctl usage: keyctl add trusted my_trusted_key "new 32 wrap_flags=0x02" @u
>
> NOTE:
> -> Setting the secure boot requirement is NOT a must.
> -> Only either of the secure boot requirement options should be set. Not
> both.
> -> All the other bits are required to be not set.
> -> Set the kernel parameter trusted.source=pkwm to choose PKWM as the
> backend for trusted keys implementation.
> -> CONFIG_PSERIES_PLPKS must be enabled to build PKWM.
>
> Add PKWM, which is a combination of IBM PowerVM and Power LPAR Platform
> KeyStore, as a new trust source for trusted keys.
>
> Signed-off-by: Srish Srinivasan <ssrish@linux.ibm.com>
> Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
> ---
> This version introduces a private pointer for backend specific fields and
> related changes specific to the PKWM backend, but defers migrating the TPM
> fields to this new framework. That will be done independently of this
> patch series.
> MAINTAINERS | 9 +
> include/keys/trusted-type.h | 7 +-
> include/keys/trusted_pkwm.h | 33 ++++
> security/keys/trusted-keys/Kconfig | 8 +
> security/keys/trusted-keys/Makefile | 2 +
> security/keys/trusted-keys/trusted_core.c | 6 +-
> security/keys/trusted-keys/trusted_pkwm.c | 190 ++++++++++++++++++++++
> 7 files changed, 253 insertions(+), 2 deletions(-)
> create mode 100644 include/keys/trusted_pkwm.h
> create mode 100644 security/keys/trusted-keys/trusted_pkwm.c
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index cf755238c429..c98f1811f836 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -14008,6 +14008,15 @@ S: Supported
> F: include/keys/trusted_dcp.h
> F: security/keys/trusted-keys/trusted_dcp.c
>
> +KEYS-TRUSTED-PLPKS
> +M: Srish Srinivasan <ssrish@linux.ibm.com>
> +M: Nayna Jain <nayna@linux.ibm.com>
> +L: linux-integrity@vger.kernel.org
> +L: keyrings@vger.kernel.org
> +S: Supported
> +F: include/keys/trusted_pkwm.h
> +F: security/keys/trusted-keys/trusted_pkwm.c
> +
> KEYS-TRUSTED-TEE
> M: Sumit Garg <sumit.garg@kernel.org>
> L: linux-integrity@vger.kernel.org
> diff --git a/include/keys/trusted-type.h b/include/keys/trusted-type.h
> index 4eb64548a74f..03527162613f 100644
> --- a/include/keys/trusted-type.h
> +++ b/include/keys/trusted-type.h
> @@ -19,7 +19,11 @@
>
> #define MIN_KEY_SIZE 32
> #define MAX_KEY_SIZE 128
> -#define MAX_BLOB_SIZE 512
> +#if IS_ENABLED(CONFIG_TRUSTED_KEYS_PKWM)
> +#define MAX_BLOB_SIZE 1152
> +#else
> +#define MAX_BLOB_SIZE 512
> +#endif
> #define MAX_PCRINFO_SIZE 64
> #define MAX_DIGEST_SIZE 64
>
> @@ -46,6 +50,7 @@ struct trusted_key_options {
> uint32_t policydigest_len;
> unsigned char policydigest[MAX_DIGEST_SIZE];
> uint32_t policyhandle;
> + void *private;
> };

Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>

>
> struct trusted_key_ops {
> diff --git a/include/keys/trusted_pkwm.h b/include/keys/trusted_pkwm.h
> new file mode 100644
> index 000000000000..4035b9776394
> --- /dev/null
> +++ b/include/keys/trusted_pkwm.h
> @@ -0,0 +1,33 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +#ifndef __PKWM_TRUSTED_KEY_H
> +#define __PKWM_TRUSTED_KEY_H
> +
> +#include <keys/trusted-type.h>
> +#include <linux/bitops.h>
> +#include <linux/printk.h>
> +
> +extern struct trusted_key_ops pkwm_trusted_key_ops;
> +
> +struct trusted_pkwm_options {
> + u16 wrap_flags;
> +};
> +
> +static inline void dump_options(struct trusted_key_options *o)
> +{
> + const struct trusted_pkwm_options *pkwm;
> + bool sb_audit_or_enforce_bit;
> + bool sb_enforce_bit;
> +
> + pkwm = o->private;
> + sb_audit_or_enforce_bit = pkwm->wrap_flags & BIT(0);
> + sb_enforce_bit = pkwm->wrap_flags & BIT(1);
> +
> + if (sb_audit_or_enforce_bit)
> + pr_debug("secure boot mode required: audit or enforce");
> + else if (sb_enforce_bit)
> + pr_debug("secure boot mode required: enforce");
> + else
> + pr_debug("secure boot mode required: disabled");
> +}
> +
> +#endif
> diff --git a/security/keys/trusted-keys/Kconfig b/security/keys/trusted-keys/Kconfig
> index 204a68c1429d..9e00482d886a 100644
> --- a/security/keys/trusted-keys/Kconfig
> +++ b/security/keys/trusted-keys/Kconfig
> @@ -46,6 +46,14 @@ config TRUSTED_KEYS_DCP
> help
> Enable use of NXP's DCP (Data Co-Processor) as trusted key backend.
>
> +config TRUSTED_KEYS_PKWM
> + bool "PKWM-based trusted keys"
> + depends on PSERIES_PLPKS >= TRUSTED_KEYS
> + default y
> + select HAVE_TRUSTED_KEYS
> + help
> + Enable use of IBM PowerVM Key Wrapping Module (PKWM) as a trusted key backend.
> +
> if !HAVE_TRUSTED_KEYS
> comment "No trust source selected!"
> endif
> diff --git a/security/keys/trusted-keys/Makefile b/security/keys/trusted-keys/Makefile
> index f0f3b27f688b..5fc053a21dad 100644
> --- a/security/keys/trusted-keys/Makefile
> +++ b/security/keys/trusted-keys/Makefile
> @@ -16,3 +16,5 @@ trusted-$(CONFIG_TRUSTED_KEYS_TEE) += trusted_tee.o
> trusted-$(CONFIG_TRUSTED_KEYS_CAAM) += trusted_caam.o
>
> trusted-$(CONFIG_TRUSTED_KEYS_DCP) += trusted_dcp.o
> +
> +trusted-$(CONFIG_TRUSTED_KEYS_PKWM) += trusted_pkwm.o
> diff --git a/security/keys/trusted-keys/trusted_core.c b/security/keys/trusted-keys/trusted_core.c
> index b1680ee53f86..2d328de170e8 100644
> --- a/security/keys/trusted-keys/trusted_core.c
> +++ b/security/keys/trusted-keys/trusted_core.c
> @@ -12,6 +12,7 @@
> #include <keys/trusted_caam.h>
> #include <keys/trusted_dcp.h>
> #include <keys/trusted_tpm.h>
> +#include <keys/trusted_pkwm.h>
> #include <linux/capability.h>
> #include <linux/err.h>
> #include <linux/init.h>
> @@ -31,7 +32,7 @@ MODULE_PARM_DESC(rng, "Select trusted key RNG");
>
> static char *trusted_key_source;
> module_param_named(source, trusted_key_source, charp, 0);
> -MODULE_PARM_DESC(source, "Select trusted keys source (tpm, tee, caam or dcp)");
> +MODULE_PARM_DESC(source, "Select trusted keys source (tpm, tee, caam, dcp or pkwm)");
>
> static const struct trusted_key_source trusted_key_sources[] = {
> #if defined(CONFIG_TRUSTED_KEYS_TPM)
> @@ -46,6 +47,9 @@ static const struct trusted_key_source trusted_key_sources[] = {
> #if defined(CONFIG_TRUSTED_KEYS_DCP)
> { "dcp", &dcp_trusted_key_ops },
> #endif
> +#if defined(CONFIG_TRUSTED_KEYS_PKWM)
> + { "pkwm", &pkwm_trusted_key_ops },
> +#endif
> };
>
> DEFINE_STATIC_CALL_NULL(trusted_key_seal, *trusted_key_sources[0].ops->seal);
> diff --git a/security/keys/trusted-keys/trusted_pkwm.c b/security/keys/trusted-keys/trusted_pkwm.c
> new file mode 100644
> index 000000000000..4f391b77a907
> --- /dev/null
> +++ b/security/keys/trusted-keys/trusted_pkwm.c
> @@ -0,0 +1,190 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (C) 2025 IBM Corporation, Srish Srinivasan <ssrish@linux.ibm.com>
> + */
> +
> +#include <keys/trusted_pkwm.h>
> +#include <keys/trusted-type.h>
> +#include <linux/build_bug.h>
> +#include <linux/key-type.h>
> +#include <linux/parser.h>
> +#include <asm/plpks.h>
> +
> +enum {
> + Opt_err,
> + Opt_wrap_flags,
> +};
> +
> +static const match_table_t key_tokens = {
> + {Opt_wrap_flags, "wrap_flags=%s"},
> + {Opt_err, NULL}
> +};
> +
> +static int getoptions(char *datablob, struct trusted_key_options *opt)
> +{
> + substring_t args[MAX_OPT_ARGS];
> + char *p = datablob;
> + int token;
> + int res;
> + u16 wrap_flags;
> + unsigned long token_mask = 0;
> + struct trusted_pkwm_options *pkwm;
> +
> + if (!datablob)
> + return 0;
> +
> + pkwm = opt->private;
> +
> + while ((p = strsep(&datablob, " \t"))) {
> + if (*p == '\0' || *p == ' ' || *p == '\t')
> + continue;
> +
> + token = match_token(p, key_tokens, args);
> + if (test_and_set_bit(token, &token_mask))
> + return -EINVAL;
> +
> + switch (token) {
> + case Opt_wrap_flags:
> + res = kstrtou16(args[0].from, 16, &wrap_flags);
> + if (res < 0 || wrap_flags > 2)
> + return -EINVAL;
> + pkwm->wrap_flags = wrap_flags;
> + break;
> + default:
> + return -EINVAL;
> + }
> + }
> + return 0;
> +}
> +
> +static struct trusted_key_options *trusted_options_alloc(void)
> +{
> + struct trusted_key_options *options;
> + struct trusted_pkwm_options *pkwm;
> +
> + options = kzalloc(sizeof(*options), GFP_KERNEL);
> +
> + if (options) {
> + pkwm = kzalloc(sizeof(*pkwm), GFP_KERNEL);
> +
> + if (!pkwm) {
> + kfree_sensitive(options);
> + options = NULL;
> + } else {
> + options->private = pkwm;
> + }
> + }
> +
> + return options;
> +}
> +
> +static int trusted_pkwm_seal(struct trusted_key_payload *p, char *datablob)
> +{
> + struct trusted_key_options *options = NULL;
> + struct trusted_pkwm_options *pkwm = NULL;
> + u8 *input_buf, *output_buf;
> + u32 output_len, input_len;
> + int rc;
> +
> + options = trusted_options_alloc();
> +
> + if (!options)
> + return -ENOMEM;
> +
> + rc = getoptions(datablob, options);
> + if (rc < 0)
> + goto out;
> + dump_options(options);
> +
> + input_len = p->key_len;
> + input_buf = kmalloc(ALIGN(input_len, 4096), GFP_KERNEL);
> + if (!input_buf) {
> + pr_err("Input buffer allocation failed. Returning -ENOMEM.");
> + rc = -ENOMEM;
> + goto out;
> + }
> +
> + memcpy(input_buf, p->key, p->key_len);
> +
> + pkwm = options->private;
> +
> + rc = plpks_wrap_object(&input_buf, input_len, pkwm->wrap_flags,
> + &output_buf, &output_len);
> + if (!rc) {
> + memcpy(p->blob, output_buf, output_len);
> + p->blob_len = output_len;
> + dump_payload(p);
> + } else {
> + pr_err("Wrapping of payload key failed: %d\n", rc);
> + }
> +
> + kfree(input_buf);
> + kfree(output_buf);
> +
> +out:
> + kfree_sensitive(options->private);
> + kfree_sensitive(options);
> + return rc;
> +}
> +
> +static int trusted_pkwm_unseal(struct trusted_key_payload *p, char *datablob)
> +{
> + u8 *input_buf, *output_buf;
> + u32 input_len, output_len;
> + int rc;
> +
> + input_len = p->blob_len;
> + input_buf = kmalloc(ALIGN(input_len, 4096), GFP_KERNEL);
> + if (!input_buf) {
> + pr_err("Input buffer allocation failed. Returning -ENOMEM.");
> + return -ENOMEM;
> + }
> +
> + memcpy(input_buf, p->blob, p->blob_len);
> +
> + rc = plpks_unwrap_object(&input_buf, input_len, &output_buf,
> + &output_len);
> + if (!rc) {
> + memcpy(p->key, output_buf, output_len);
> + p->key_len = output_len;
> + dump_payload(p);
> + } else {
> + pr_err("Unwrapping of payload failed: %d\n", rc);
> + }
> +
> + kfree(input_buf);
> + kfree(output_buf);
> +
> + return rc;
> +}
> +
> +static int trusted_pkwm_init(void)
> +{
> + int ret;
> +
> + if (!plpks_wrapping_is_supported()) {
> + pr_err("H_PKS_WRAP_OBJECT interface not supported\n");
> + return -ENODEV;
> + }
> +
> + ret = plpks_gen_wrapping_key();
> + if (ret) {
> + pr_err("Failed to generate default wrapping key\n");
> + return -EINVAL;
> + }
> +
> + return register_key_type(&key_type_trusted);
> +}
> +
> +static void trusted_pkwm_exit(void)
> +{
> + unregister_key_type(&key_type_trusted);
> +}
> +
> +struct trusted_key_ops pkwm_trusted_key_ops = {
> + .migratable = 0, /* non-migratable */
> + .init = trusted_pkwm_init,
> + .seal = trusted_pkwm_seal,
> + .unseal = trusted_pkwm_unseal,
> + .exit = trusted_pkwm_exit,
> +};
> --
> 2.47.3
>

BR, Jarkko